http://marine.rutgers.edu/~francis/pres/Francis_Vavrus_2012GL051000_pub.pdf
3. Conclusions
[14] In summary, the observational analysis presented in this study provides evidence supporting two hypothesized mechanisms by which Arctic amplification – enhanced Arctic warming relative to that in mid-latitudes – may cause more persistent weather patterns in mid-latitudes that can lead to
extreme weather. One effect is a reduced poleward gradient in 1000-500 hPa thicknesses, which weakens the zonal upper-level flow. According to Rossby wave theory, a weaker flow slows the eastward wave progression and tends to follow a higher amplitude trajectory, resulting in slower
moving circulation systems. More prolonged weather conditions enhance the probability for extreme weather due to drought, flooding, cold spells, and heat waves. The second effect is a northward elongation of ridge peaks in 500 hPa waves, which amplifies the flow trajectory and further
exacerbates the increased probability of slow-moving weather patterns. While Arctic amplification during autumn and winter is largely driven by sea-ice loss and the subsequent transfer of additional energy from the ocean into the high-latitude atmosphere, the increasing tendency for highamplitude
patterns in summer is consistent with enhanced warming over high-latitude land caused by earlier snow melt and drying of the soil. Enhanced 500-hPa ridging observed over the eastern N. Atlantic is consistent with more persistent high surface pressure over western Europe. This effect has been implicated as contributing to record heat waves in Europe during recent summers [Jaeger and Seneviratne, 2011].
[15] Can the persistent weather conditions associated with recent severe events such as the snowy winters of 2009/2010 and 2010/2011 in the eastern U.S. and Europe, the historic drought and heat-wave in Texas during summer 2011, or record-breaking rains in the northeast U.S. of summer 2011
be attributed to enhanced high-latitude warming? Particular causes are difficult to implicate, but these sorts of occurrences are consistent with the analysis and mechanism presented in this study. As the Arctic sea-ice cover continues to disappear and the snow cover melts ever earlier over vast regions of Eurasia and North America [Brown et al., 2010], it is expected that large-scale circulation patterns throughout the northern hemisphere will become increasingly influenced by Arctic Amplification. Gradual warming of the globe may not be noticed by most, but everyone – either directly or indirectly – will be affected to some degree by changes in the frequency and intensity of extreme weather events as greenhouse gases continue to accumulate in the atmosphere. Further research will elucidate the types, locations, timing, and character of the weather changes, which will provide valuable guidance to decision-makers in vulnerable regions.
